The present invention relates to electronic semiconductor devices and fabrication methods, and, more particularly, to Schottky barrier diodes including diodes formed in integrated circuits.
Schottky barrier diodes are widely used in integrated circuits in applications such as decoupling devices in digital circuits (silicon bipolar and gallium arsenide MOSFET) and as clamping devices to prevent heavy saturation of bipolar transistors. Generally, a Schottky barrier diode is formed by deposition of suitable barrier metal into a contact opening through a silicon dioxide insulating layer down to bare silicon. The barrier metal may be reacted with the silicon to form a silicide-to-silicon junction (for example Pt is deposited and reacted to form transistor clamping and Ti is deposited and reacted to form TiSi2 and is used as a low barrier diode for logic circuits) or may be left unreacted and form a metal-to silicon junction (for example TiW is used as a low barrier diode and Al as a high barrier diode on n-type silicon). Note that the reaction with silicon: that is, a metal is uniformly deposited but only the portion in contact with bare silicon reacts so the unreacted metal away from the silicon can be selectively removed. Of course, a silicide could be directly deposited which would avoid the need for reaction of the metal with the silicon but would not yield a self-aligned structure.